SPERMATOPHYTES 



191 



Sporophyte. — The sporophyte body consists of a tuberous or columnar 

 stem, covered by an armor of leaf bases, and bearing a crown of large 

 branched leaves and an apparently terminal strobilus (figs. 433-437)- 

 All the stems are tuberous when young, but in some species the tuberous 

 body passes into the columnar, which in certain species of Cycas reaches 



Fig. 434. — Dioon cdulc (Mexican). — After Chamberlain. 



a height of 10 or even 20 m. (fig. 433). In those forms with the per- 

 sistently tuberous habit, the stem is sometimes subterranean and very 

 small (fig. 437). While the stem usually appears to terminate in a 

 single strobilus, the strobili are in fact lateral, although close to the 

 apex, and a succession of them may appear near the stem tip. In fact, 

 in an African form strobili have been observed arising in a cycle about 

 the vegetative point. It will be remembered that the strobili of Ben- 



